The Institute for Reference Materials and Measurements (IRMM) of the Joint Research Centre (JRC), a Directorate-General of the European Commission, operates the Community Reference Laboratory for Heavy Metals in Feed and Food (CRL-HM). One of its core tasks is to organise interlaboratory comparisons (ILCs) among appointed National Reference laboratories (NRLs). This report presents the results of the fourth ILC of the CRL-HM which focused on the determination of total Cd, Pb, As, Hg and methylmercury (related to dry mass) in seafood.
The test material used in this exercise was the Certified Reference Material (CRM) TORT-2, lobster hepatopancreas, of the National Research Council of Canada. The material was rebottled and relabelled to prevent recognition by the participants and it was dispatched in the first half of May 2008. Each participant received one bottle containing approximately 20g of test material. Thirty-four participants from twenty-six counttries registered to the exercise of which thirty-three sets of results were reported for Cd and total mercury, thirty-two for Pb, twenty-seven for arsenic and four for methylmercury. One laboratory reported two stes of values for Cd, Pb, Hg and As obtained with two different techniques, respectively. The Assigned values were the certified values taken from the TORT-2 certificate.
The uncertainties of the respective assigned values, uref, were taken directly from the CRM certificate as provided by the producer. Participants were invited to report the uncertainty on their measurements. This was done by all the laboratories taking part in the exercise.
Laboratory results were rated with z and zeta scores in accordance with ISO 13528. Standard deviation for profficiency assessment (also called target standard deviation) were calculated, using the modified Horwitz equation, and were 9.76% for total Cd, 18.74% for total Pb, 10% for total As, 19.48% for total Hg and 21.24% for methylmercury.